This application is based on and claims the priority under 35 U.S.C. xc2xa7119 of German Patent Applications 100 47 518.3, filed on Sep. 22, 2000 and 100 59 914.1, filed on Dec. 1, 2000, the entire disclosures of which are incorporated herein by reference.
The invention relates to an arrangement for capturing and recovering spacecraft, as well as transporting the recovered spacecraft in orbit, returning the spacecraft to earth, or leading the spacecraft into a targeted destruction through re-entry and burning-up in the earth""s atmosphere, by means of a powered recovery craft, preferably in the form of a satellite equipped with a coupling mechanism between the recovery craft and the spacecraft to be recovered.
There are several situations in which it becomes necessary or desirable to recover, capture and transport a defective or expended satellite. For example, it may be necessary or desired to move the spacecraft to a different orbit or trajectory, or lead the spacecraft into a return to earth, or to a guided and targeted destructive re-entry trajectory that will ensure a complete destruction of the spacecraft by burning-up in the earth""s atmosphere, or by returning to earth at an impact location in an ocean or in an uninhabited land area.
Recovery measures are necessary when the position and orbit or trajectory of the defective or expended spacecraft would possibly impair or endanger the optimal operation of some other spacecraft or space system. A defective spacecraft may have a negative influence on other spacecraft or satellite systems, for example, if the defective satellite has not reached its original intended target position in an intended orbit, or has drifted out of that intended position, and as a result, the defective satellite is positioned in a reception and transmission zone of other systems and thus interferes with these other systems through its electro-magnetic characteristics or a simple shading effect.
Recovery measures are also necessary if a spacecraft is in a decaying orbit and will re-enter the earth""s atmosphere in a manner whereby parts of the spacecraft, which have not completely burned-up in the earth""s atmosphere, will crash or impact onto the earth in inhabited areas, thereby possibly endangering persons and property. In other words, a dangerous uncontrolled partial incineration of the defective spacecraft in the earth""s atmosphere arises if the spacecraft follows a re-entry path with an improper re-entry angle, so that a complete burning-up or incineration of the spacecraft in the atmosphere cannot be achieved. In this case, it is possible that the spacecraft or parts thereof will impact the earth at an undesired impact location, which would endanger persons and property.
All of the above problems can be avoided through the appropriate capture, recovery and repositioning or transporting of the defective or expended spacecraft. Throughout this specification, the term spacecraft refers to satellites, space stations and components thereof, launch vehicles, orbiter vehicles, orbiting xe2x80x9cspace junkxe2x80x9d, or any other body orbiting or flying in space.
It has been found in practice, that it is rather complicated and costly to capture, recover and transport-away defective spacecraft or spacecraft that have reached the end of their service life, such as rocket parts, burned-out rocket stages, satellites, space station elements and the like. Previously it has not been possible to recover and transport spacecraft that are themselves not maneuverable, without direct human intervention and active control. It has been especially difficult to achieve the actual capture and coupling of the defective or expended spacecraft to the recovery craft. The known coupling measures require complex, high-precision positioning and engagement of the respective coupling means, which is rather difficult to achieve in practice.
U.S. Pat. No. 6,017,000 (Scott) discloses an apparatus and methods for coupling a satellite or other spacecraft to a powered recovery craft. The coupling mechanism is designed and constructed to couple the two spacecraft to each other only in relation to a high-precision close approach or proximity operation of the recovery spacecraft to the defective spacecraft. It is not possible to achieve coupling in the event of substantial deviations or distances between the two spacecraft.
German Patent 32 15 229 discloses a coupling apparatus for guiding and connecting together two spacecraft, while being able to achieve a coupling even in the event of certain deviations of position or alignment between the two spacecraft. Namely, the disclosed apparatus compensates deviations within a certain spatial angular range as well as a relative offset or shifting, by means of funnel arrangements and springs. The disclosed coupling apparatus includes a coupling funnel with a locking trap at the bottom of the funnel on one spacecraft, and a telescoping rod having a head piece provided with a catch or detent pawl that is extendable from the second spacecraft. The telescoping rod is supported by springs, a light emitting device is arranged on the funnel floor or bottom, and an optical sensor is provided on the head piece of the telescoping rod, whereby the light emitting device and the optical sensor cooperate to provide signals for controlling the orientation of the telescoping rod relative to and into the coupling funnel. The disclosed arrangement is not suitable for taking up and transmitting substantial tension forces between the two spacecraft.
Other conventionally known spacecraft recovery systems mostly rely on robot elements such as gripper mechanisms for coupling onto the spacecraft that is to be recovered. Such robot elements must be precisely guided to the target coupling location and must also compensate for dynamic relative movements and oscillations. This generally requires a complex computer-supported regulation and control circuit, which must in turn be monitored and influenced or steered from the ground control station.
It is an object of the invention to provide a structurally simple, universally applicable coupling arrangement of the above described general type, in order to achieve an efficient and economical handling and operation thereof, as well as enabling the transmission of tension forces therethrough for transporting a second spacecraft with a first spacecraft. It is another object of the invention to provide a robust, trouble-free, simple structure that achieves automatic self-alignment for carrying out the coupling within a large tolerance or deviation range. The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as apparent from the present specification.
The above objects have been achieved according to the invention in a system including a first spacecraft, a second spacecraft, and a coupling arrangement for coupling together the two spacecraft. According to the invention, the coupling arrangement is improved in that it comprises a mast-like holding element (or coupling mast), which is connected to the first spacecraft by a (releasable mount provided at a first end of the holding element, and that captures, engages and is connected to the second spacecraft by movable or adjustable spreader elements in the form of at least three spreader arms provided at or proximate to a second end of the holding element. In this context, xe2x80x9cproximate to the second endxe2x80x9d means, for example, within one third of the total length of the holding element from the termination of the second end thereof. The spreader elements are controlledly movable, to be selectively moved between a retracted condition and an extended condition.
In the retracted condition, the spreader arms are pivoted relatively radially inwardly toward the extension axis of the holder element. On the other hand, in the extended condition, the spreader arms are spread radially outwardly from the extension axis of the holder element, so as to engage into a corresponding interface ring provided on the second spacecraft, i.e. the spacecraft to be recovered. In the deployed, extended or spread-out condition, the spreader elements reach and engage into a recess and/or behind an overhanging rim of the interface ring so as to establish especially a tension-transmitting connection. A spring arrangement braces against the second satellite, especially in a direction parallel to the lengthwise axis of the holder element, for fixing the spreader elements into the interface ring by means of an elastic spring-biased bracing effect.
The invention provides a simple embodiment of a capture and arresting apparatus, for achieving a coupling of a recovery craft to a spacecraft that is to be recovered. In comparison to conventional recovery systems using grippers or other coupling means, the inventive coupling system has the advantage of a mechanically simple and thus trouble-free and interference-free construction.
In order to achieve a good adaptation and compensation of a rather large range of deviations or mis-alignments between the two spacecraft, the invention provides that the coupling head including the spreader elements is essentially self-centering and self-aligning in the interface ring, and that a large distance between the two spacecraft can be bridged and coupled because the mast-like holder element comprises an extendable telescoping pipe. The telescoping action of the inner pipe and outer pipe can also automatically pivotally spread out and thereby deploy the spreader elements that couple into engagement with the interface ring.
To ensure a well-controlled positioning and coupling of the coupling head into the interface ring, the holder element is initially rigidly connected to the recovery craft by a releasable rigid mount. On the other hand, in order to decouple the body dynamics of the two spacecraft from each other, the rigid mount is released from the recovery craft after the coupling connection has been established. Thereby, the holder element is no longer rigidly mounted or connected to the recovery craft. Instead, an extendable cable arrangement or the like provides a flexible tension-transmitting connection between the coupling arrangement and the recovery craft, without transmitting any forces other than direct tension forces. To achieve a simple release or decoupling, the connection of the holder element to the recovery craft can be provided by pyrotechnically explodable bolts or the like, or any releasable connectors.